Update dependencies and package-lock

Bump direct dependencies (@cloudflare/ai-chat 0.2.5→0.2.6, agents 0.8.6→0.8.7, ai 6.0.138→6.0.141, @cloudflare/vite-plugin 1.30.1→1.30.2, wrangler 4.77.0→4.78.0) and regenerate package-lock.json. The lockfile reflects many transitive updates (ai-sdk packages, base-ui, floating-ui, tslib entries, miniflare, framer-motion/motion packages, katex, marked, path-to-regexp, react-day-picker, tailwind-merge, semver reorganizations, zod-to-json-schema, partyserver, and others) to align resolved versions.

Author: threepointone